BACKSTEPPING CONTROL OF NONLINEAR ROLL MOTION FOR A TRAWLER WITH FIN STABILIZER

A backstepping control design procedure for nonlinear fin roll control of a trawler is presented in this paper. A roll equation consisting of linear and nonlinear damping and restoring moment on the roll response is expressed. Flow analyses are carried out for a scaled model of trawler type fishing vessel including fin stabilizers on both sides of the hull. The fin stabilizer geometry is chosen as NACA 0015 foil section which is widely used in the literature. The flow analyses are performed by using a commercial computational fluid dynamics (CFD) software based on finite volume method. The flow problem is modeled in a 3-dimensional manner while the flow is considered as steady, incompressible and fully turbulent. The numerical model consists of the ship wetted surface and the fin stabilizer in order to investigate the hull-fin interaction. Non-dimensional lift coefficients of the fin stabilizer for different angles of attack are gained. Both controlled and uncontrolled roll motions are examined and simulated in time domain for the maximum lift coefficient. Backstepping controller for roll motion has given a rapid and precise result.

Fluid Resonance Between Twin Floating Barges with Roll Motion Under Wave Action

The wave-induced fluid resonance between twin side-by-side rectangular barges coupled with the roll motion of the twin barges is investigated by both numerical simulation and physical model test. A 2D numerical wave flume, based on an open source computational fluid dynamics (CFD) package OpenFOAM, is applied for the numerical simulation. After numerical validations and convergent verifications, the characteristics of the fluid resonance in the gap between the twin rolling side-by-side barges are examined. The resonant frequency of the oscillating fluid in the gap between the twin rolling barges decreases compared with that between the twin fixed barges. Generally, the twin barges roll in the opposite directions, and their equilibrium positions lean oppositely with respect to the initial vertical direction. A physical model test is carried out for a further investigation, in which the twin barges are set oppositely leaning and fixed. From the present experimental results, a linear decrease of the resonant frequency with the increasing leaning angle is found. Combined with the numerical results, the deflection of the equilibrium positions of the twin barges is a relevant factor for the resonant frequency. Besides, the effects of the gap width and incident wave height on the fluid resonance coupled with roll motion are examined.

Research on the effect of car’s roll motion on the aerodynamic characteristics of high-speed car

The main purpose of this study is to study the aerodynamic mechanism of periodic roll motion of car body and provide engineering reference for car design and safety evaluation. A simplified roll motion model is established based on a real car model. The two-wheel centerline of the left-wheel symmetrical section is considered as the roll axis, and the overset mesh method was used to model the sinusoidal roll motion of the car. According to the experimental data, the frequency and maximum roll angle were set to be 10 Hz and 2.2°, respectively. A transient numerical solver based on the detached-eddy simulation method is employed. The accuracy of the numerical method is validated by means of the wind tunnel test. Due to the asymmetry of the movement, the aerodynamic change of the roll motion was obvious. It is found that the roll motion is closely related to the aerodynamic characteristics of the car. Because of the hysteresis effect, the phase of aerodynamic force on the car shifts and the most dangerous position of the car is obtained. In addition, the aerodynamic differences of the car parts are found, and the wake is analyzed in detail.

ANALISA TITIK KRITIS GERAKAN ROLL KAPAL TRIMARAN UNTUK DIAPLIKASI PADA KAPAL IKAN PURSE SEINE

The marine fisheries catching and processing industry are considered vulnerable to the effects of extreme weather at sea. Global warming effects and El Nino and La Nina have a significant impact on the upwelling process, which impacts the lifestyle and environment of marine biota, including pelagic fish, which is one of the most important contributors to the shipping industry. Extreme weather conditions, with wave heights ranging from 1 to 5 meters, dominate the waters of Maluku. In extreme sea conditions, most fishers choose not to go fishing, not because there are no fish at the fishing grounds, but to avoid mishaps at sea. This research aimed to analyze the critical point of ship roll motion and ship stability. The hull shape employed in this study was a monohull fishing vessel and a trimaran fishing vessel with the same displacement of 21,1 tons. In extreme weather conditions, the Maxsurf software was used to analyze the ship's response, especially the critical point of the ship's roll motion. The I.M.O. Standard was utilized to calculate the ship's stability. The operational speed of the ship was v = 3 knots, with fluctuations in wave angle of incidence between 00 - 1800. Wave heights of 1,0; 2,0; 3,0, and 0,4 meters represent extreme weather conditions in Maluku waters' fishing grounds. The findings revealed that the trimaran hull type had better stability where the inclination angle of trimaran vessel stability was 480 while the monohull was 410. The trimaran fishing vessel was able to withstand a wave height of 3 meters with an inclination angle of 32,560. In comparison, the monohull fishing vessel was able to survive at a wave height of 2 meters with an inclination angle of 24,690. Monohull fishing vessel had a maximum limit of roll motion at wave directions 82 and 99 with a wave height of 3 m, and it reached at the critical point at angles of 43 and 138, at the height of 4 m. Meanwhile, the trimaran fishing vessel had a critical point at a wave angle of 760 and 1000 with a wave height of 4 meters. In the area between those two angles, monohull and trimaran fishing vessels will lose the balance (stability) of the roll motion, resulting in capsize.

Experimental Investigation of FPSO Roll Motion Response Coupled with Sloshing in a Pair of Two Row Cargo Tanks

Floating Production Storage and Offloading Units (FPSOs) will continue to be in high demand because of their numerous advantages; such as, their ability to offer early production and operate in ultra-deep water locations, while remaining easy to relocate to meet changing needs. By design, slack cargo tanks are almost always present in FPSOs due to continuous loading and offloading operations; however, the presence of slack cargo impacts the seakeeping stability abilities of FPSOs. There are limited published experimental data on coupled sloshing with seakeeping of stationary vessels, and existing studies on this have focused on single row cargo tanks which is seldom the case in FPSOs. The aim of this paper is to study roll motion coupled with sloshing in partially-filled pair of two-row tanks of a stationary FPSO model exposed to regular beam waves. The model tests was performed in the Davidson Laboratory towing tank at Stevens Institute of Technology. The FPSO model response in roll was measured, and the time histories of sloshing oscillation were measured on the starboard and port side of one of the stern cargo tanks. The results show that varying internal cargo sloshing leads to unpredictable motion response of floating vessels that should be accounted for in the design and offloading operations of FPSO.